1. Field of the Invention
The present invention relates to a control system and method for a hydraulic working machine which performs works by driving an actuator with use of hydraulic fluid.
2. Description of the Related Art
If an operating lever for controlling an actuator speed in a hydraulic working machine is operated suddenly, the actuator speed will change suddenly, causing a violent impact or vibration. In an effort to solve this problem, there has been proposed a technique in which a throttle is inserted in a pilot line for controlling a main flow control valve to delay the response of the flow control valve relative to a lever operation. With this technique, however, the follow-up performance of the actuator speed relative to a lever operation is deteriorated and so is the operability. As a countermeasure there is known a technique in which a variable throttle is used as the throttle inserted in the pilot line for the flow control valve or a pipe is provided for communication between both side pipes which connect the actuator and the control valve with each other.
However, in the former case, if the variable throttle should fail, the motion of the control valve is deteriorated, causing problems in operation such as the actuator becoming difficult to be braked. Also in the latter case, the front and rear of the actuator become communicated, giving rise to problems in operation such as the actuator no longer coming to a stop. Further, since a bypass passage for communication between both side pipes is formed, the amount of hydraulic fluid fed to the actuator decreases and so does the speed.